Analog Devices Inc. AD7799BRU

Overview

AD7799BRU from Analog Devices is a 24-bit, low-noise, low-power Σ-Δ analog-to-digital converter with integrated instrumentation amplifier, three differential input channels, and on-chip reference detection-designed for high-precision DC measurements in weigh scales, pressure sensors, and strain gauge interfaces operating from 2.7 V to 5.25 V supply.

For engineers reviewing the AD7799BRU datasheet, AD7799BRU pinout, AD7799BRU application, or AD7799BRU equivalent, this page delivers verified specifications including 27 nV rms noise at 4.17 Hz, 380 µA typical current draw, 16-lead TSSOP package mapping, simultaneous 50/60 Hz rejection, and programmable gain up to 128-enabling direct sensor interface without external signal conditioning.

Technical Context

The AD7799BRU implements a fully integrated analog front end with a chopper-stabilized instrumentation amplifier feeding a 24-bit Σ-Δ modulator and digital filter. Its architecture supports software-programmable update rates from 4.17 Hz to 470 Hz and includes internal clock oscillator, burnout currents, and low-side power switch (PSW) for sensor excitation control.

It features independent AVDD (analog) and DVDD (digital I/O) supplies, enabling mixed-voltage system interfacing, and supports SPI/QSPI/MICROWIRE-compatible 3-wire serial communication with Schmitt-triggered SCLK for noise immunity in industrial environments.

Key Specifications

Pinout & Package

AD7799BRU is housed in a 16-lead TSSOP package (4.4 mm × 5.0 mm, 0.65 mm pitch) with exposed pad for thermal enhancement. Pin functions are validated per Analog Devices Rev. B datasheet Figure 5 and Table 4.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-precision sigma-delta ADC applications.

Compared with AD7799BRU, AD7124-4BRUZ offers greater integration and channel count at higher power efficiency, while ADS124S08IPWR trades ultra-low noise for speed and simplified layout-making AD7799BRU optimal for static, ultra-high-resolution DC measurements where in-amp integration and sub-30 nV noise are decisive.

Availability

AD7799BRU is available at Aetrix Electronics and suitable for weigh scales, pressure transmitters, and portable instrumentation requiring stable component supply, long-term lifecycle support, and traceable sourcing for medical and industrial OEMs.

Supply support for AD7799BRU includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA, with design centers worldwide and over 50 years of precision converter innovation.

The AD7799BRU belongs to Analog Devices' precision Σ-Δ ADC product line, engineered specifically for low-power, high-resolution DC measurement applications in industrial, medical, and scientific instrumentation where noise, drift, and integration are critical.

FAQ

What is the maximum guaranteed resolution of AD7799BRU at 4.17 Hz update rate?

The AD7799BRU guarantees 24-bit no-missing-codes performance at update rates below 242 Hz. At 4.17 Hz with gain = 64, it achieves 21.5 effective bits (20.5 peak-to-peak bits) per Table 8-delivering true 24-bit capability for static, high-fidelity DC measurements. This resolution is confirmed by Analog Devices' Rev. B datasheet under standard test conditions with 2.5 V reference and bipolar input range.

Does AD7799BRU require an external crystal or oscillator?

No, AD7799BRU does not require an external crystal or oscillator. It integrates a factory-trimmed internal clock oscillator operating at 64 kHz ±3%, which drives the Σ-Δ modulator and digital filter. This eliminates external timing components, reduces PCB footprint, and improves reliability-confirmed in the "INTERNAL CLOCK" section of the Rev. B datasheet.

Can AD7799BRU interface directly with a 3.3 V microcontroller SPI bus?

Yes, AD7799BRU supports direct interface with 3.3 V microcontrollers via its independent DVDD supply pin. When DVDD = 3.3 V, logic thresholds are specified for VINH ≥2.0 V and VINL ≤0.8 V (Table 1), and DOUT/RDY/DIN/SCLK meet 3.3 V CMOS levels. The Schmitt-triggered SCLK further enhances noise immunity in mixed-signal systems.

What is the function of the PSW pin on AD7799BRU?

The PSW (low-side power switch) pin on AD7799BRU is an integrated N-channel MOSFET with RON ≤9 Ω (at AVDD = 3 V) and 30 mA continuous current rating. It enables controlled excitation of resistive sensors (e.g., strain gauges, RTDs) and automatic power gating-eliminating the need for discrete switches and reducing system complexity and leakage paths.

How does AD7799BRU handle reference voltage loss detection?

AD7799BRU implements hardware-based reference detect via its REFIN(+) and REFIN(−) inputs. If the applied reference voltage falls below 0.3 V, the NOXREF bit in the status register is asserted-allowing firmware to halt conversions and trigger fault handling. This behavior is documented in the "REFERENCE DETECT" section and Table 1 of the Rev. B datasheet.